This research is an attempt to define the regulation of reporduction in a single lepidopteran species, i.e., the Monarch butterfly, Danaus plexxipus. It consists of structural, biochemical, and experimental investigations of the role played by the environment, the neuroendocrine system, and the reproductive glands in the regulation of Monarch gametogenesis, reproductive behavior, and reproductively oriented metabolism. BIBLIOGRAPHIC REFERENCES: Herman, W.S., and P. Peng. 1976. Juvenile hormone stimulation of sperm activator production in male Monarch butterflies. J. Insect Physiol. in press. Herman, W.S., and J.F.Barker. 1976. Ecodysterone antagonism, mimicry, and synergism of juvenile hormone action on the Monarch butterfly reproductive tract. J. Insect Physiol., in press.